Improvements and extensions of pyroelectric calorimetry for study of heat production by milligram weight biochemical and cellular systems are under development. Pyroelectric calorimetric studies of phototransduction in frog retinas are being extended to low light exposures and to retinas that have been subjected to sudden changes in their fluid environment. A series of new compounds have been synthesized to be useful as elemental standards for estimating water content and transmembrane potentials in retinal and brain cells. Distributions of these compounds is being studies by electron energy-loss spectrometry. The metabolism of esterified membrane-permeable fluorescent calcium indicator dyes is being studied by high-pressure liquid chromatography and mass spectrometry, with the aim of explaining the uneven cellular distribution of the dyes and the presence of fluorescent but calcium- insensitive forms in retinal photoreceptors.